Comparison of rice grain qualities as influenced by organic and conventional farming systems

From 1994 through 1996, qualities of rice grains cultivated under organic and conventional farming systems have been compared at 13 different locations in Japan with respect to their appearances, indices of the eating quality, mineral content, and shelf life. At each location, the organically managed paddy and conventionally managed paddy were adjacent to each other and managed by almost the same farmers. The results of the paired t-tests showed that statistically significant differences in qualities of organic and conventional rice grains were found in 1994 (n = 13), 1996 (n = 13), and a total of three years (n= 39). The organically grown rice had higher Mg/(K . N), zinc content, and embryo activity during storage and lower imperfect rice kernel ratio, nitrogen content, potassium content, and calcium content than the conventionally grown rice. Among these indices, the lower nitrogen content, higher Mg/(K . N), lower potassium content, and higher zinc content of the organically grown rice could be explained because of the lower nitrogen application in organic farming systems than in conventional farming systems. Furthermore, it was found that the organic paddies contained higher available silica than the conventional paddies did statistically, at significant levels at all the locations. This may contribute to the inhibition of nitrogen accumulation in organic rice grains.